This invention relates to polymer/polyol compositions and to polyurethanes utilizing such compositions.
Polymer/polyol compositions suitable for use in producing polyurethane foams, elastomers and the like are known materials. Such compositions can be produced by polymerizing one or more ethylenically unsaturated monomers dissolved or dispersed in a polyol in the presence of a free radical catalyst. These polymer/polyol compositions have the valuable property of imparting to, for example, polyurethane foams and elastomers produced therefrom, higher load-bearing properties than are provided by the corresponding unmodified polyols.
There are a number of prior disclosures relating to production of polymer/polyol compositions. The basic patents in the field are Stamberger U.S. Pat. No. Re. 28,715 (reissue of U.S. Pat. No. 3,383,351) and U.S. Pat. No. Re. 29,118 (reissue of U.S. Pat. No. 3,304,273). Other prior disclosures include: British Pat. No. 1,126,025; Scharf et al. Canadian Pat. No. 735,010; Kuryla Canadian Pat. No. 785,835; Pizzini et al. U.S. Pat. No. 3,652,639; Pizzini et al. U.S. Pat. No. Re. 29,014 (reissue of U.S. Pat. No. 3,823,201); Patton, Jr., et al. U.S. Pat. No. 3,950,317; Ramlow et al. U.S. Pat. No. 3,953,393; DeWald U.S. Pat. No. 3,655,553; Fabris et al. U.S. Pat. No. 3,850,861; Priest et al. U.S. Pat. No. 4,208,314; Simroth U.S. Pat. No. 4,104,236; Shah U.S. Pat. No. 4,148,840; Shah U.S. Pat. No. 4,119,586; Shook et al. U.S. Pat. No. 4,172,825; Drake et al. U.S. Pat. No. 4,198,488; Preston et al. U.S. Pat. No. 4,153,643; Japanese Pat. No. 48-101494; and Japanese Pat. No. 52-80919/75.
The polymer/polyol compositions that found initial commercial acceptance were primarily compositions produced using acrylonitrile. Such compositions were somewhat higher in viscosity than desired in some applications. Further, such compositions were at least primarily used commercially in producing foams under conditions such that the heat generated during foaming is readily dissipated (e.g.--the foams have a relatively thin cross-section) or under conditions such that relatively little heat is generated during foaming. When polyurethane foams were produced under conditions such that the heat generated during foaming was not readily dissipated, severe foam scorching usually resulted. Later, polymer/polyol compositions produced from acrylonitrile-methylmethacrylate monomer mixtures were commercialized and were convertible to polyurethane foams having reduced scorch.
More recently, polymer/polyol compositions produced from acrylonitrile-styrene monomer mixtures have been used commercially. Use of low ratios of acrylonitrile-to-styrene in the monomer mixture affords polymer/polyols that do not give rise to a scorch problem. But it is increasingly difficult to make satisfactorily stable polymer/polyols as the ratio of acrylonitrile to styrene is reduced to the desired levels.
The development of sophisticated, high speed and large volume equipment, machines and systems for handling, mixing and reacting polyurethane-forming ingredients has created the need for highly stable polymer/polyols. At one time, there was not much concern for the seediness, viscosity or filterability of polymer/polyols in actual commercial practice. However, the state of the art of polyurethane production has now advanced to the point where these considerations are very important in many applications. There is now much concern with filterability, seediness, and viscosity; and polymer/polyols must meet certain minimum requirements in order to be capable of being processed in the sophisticated foam equipment now used. Typically, the prime requirement is that the polymer/polyols possess sufficiently small particles so that filters, pumps and the like do not become plugged or fouled in relatively short periods of time.
While somewhat simplified, the commercial processability of a particular polymer/polyol comes down to its viscosity and stability against phase separation. Lower viscosities are of substantial practical and economic significance due to the ease of pumping and metering as well as ease of mixing during the formation of polyurethanes. Stability is a prime consideration in insuring that the polymer/polyols can be processed in commercial production equipment without the necessity of additional mixing to insure homogeneity.
In addition to the monomer ratio in acrylonitrile-styrene polymer/polyols, other recognized factors that affect product stability include polyol molecular weight and polymer content.
In producing polymer/polyols for use in certain polyurethane elastomer applications, relatively low molecular weight polyols are typically utilized to provide the requisite product stiffness. However, it has been found that it is increasingly difficult to make satisfactorily stable polymer/polyols as the molecular weight of the polyol is decreased.
Still other applications could desirably utilize polyurethane foams and elastomers with even higher load-bearings capacities than can be currently provided using available polymer/polyols. However, it has been found that it is increasingly difficult to make satisfactorily stable polymer/polyols as the amount of polymer is increased.
U.S. Pat. No. 4,208,314 to Priest et al. discloses low viscosity polymer/polyols made from acrylonitrile-styrene monomer mixtures. These polymer/polyols can be converted to low density, water blown polyurethane foams having reduced scorch, especially when the acrylonitrile to styrene ratio is relatively low. The Priest et al. patent also provides a process for making polymer/polyols whereby the particulate nature of the product is considerably improved, compared to polymer/polyols prepared by prior processes. Using prior procedures, such as the one disclosed in Canadian Pat. No. 735,010, polymer/polyols formed from such monomer mixtures usually contained excessive amounts of large granules. The improved process provided by Priest et al. includes, in general, maintaining a low monomer concentration throughout the reaction mixture during the polymerization.
U.S. Pat. No. 4,104,236 to Simroth discloses a substantial further improvement in forming polymer/polyols made from acrylonitrile-styrene monomer mixtures, which enables selection of the polymer content to provide a polymer/polyol having satisfactory stability when a polyol of given molecular weight and a monomer mixture having a ratio of accrylonitrile to styrene within a certain range are used. The Simroth patent also highlights the fact that satisfactory product stability is not obtained when many combinations of otherwise desirable composition parameters are used.
U.S. Pat. No. 4,172,825 to Shook et al. discloses further improvements in the formation of polymer/polyols. As discussed therein, polymer/polyol compositions exhibiting outstanding properties can be made by utilizing a specific type of peroxide catalyst, namely t-alkyl peroxyester catalysts. By utilizing this specific type of catalyst, polymer/polyols can be produced on a commercial basis which have outstanding properties, such as filterability in processing, yet which allow either the polymer or the styrene content to be increased. Also, polymer/polyols can be produced on a commercial scale with polyols having a molecular weight lower than had been used prior to this invention.
A further improvement in the formation of polymer/polyols is provided by U.S. Pat. No. 4,148,840 to Shah, which discloses a process for producing highly stable and filterable polymer/polyol compositions by polymerizing the monomer or monomers in situ in a polyol mixture that includes a minor amount of preformed polymer/polyol.
Yet another improvement is disclosed in U.S. Pat. No. 4,119,586 to Shah, which discloses a process for producing highly stable polymer/polyol compositions by polymerizing the monomer or monomers in situ in a polyol mixture that includes a major amount of a low molecular weight polyol and a minor amount of high molecular weight polyol.
U.S. Pat. No. 4,242,249 to VanCleve et al. discloses yet another approach to producing stable polymer/polyols in cases where the composition parameters are such at conventional processes would not usually afford a stable product. In the process disclosed by this patent, the monomer mixture is polymerized in a polyol that contains a minor amount of a preformed stabilizer that is tailored to the monomer mixture used. The stabilizer is a copolymer comprised of an anchor portion that is a polymer of the monomer mixture, and a solvatable portion consisting of a propylene oxide polymer having a number average molecular weight of at least about 800.
It has been recognized that the stability of polymer/polyols requires the presence of a minor amount of a graft or addition copolymer which is formed in situ from the polymer and polyol. Some prior approaches have thus been directed to incorporation of amounts of unsaturation to the polyol in addition to that inherently present in the polyoxyalkylene polyols typically used in forming polymer/polyols in the belief that improved stability will result due to an increased amount of an addition copolymer stabilizer expected to be formed. U.S. Pat. Nos. 3,652,639, 3,823,201, and 3,850,861, British Pat. No. 1,126,025, and Japanese Pat. Nos. 52-80919 and 48-101494 all utilize this approach.
U.S. Pat. No. 3,850,861 thus discloses the in situ polymerization of ethylenically unsaturated monomers in an unsaturated polyol. Suitable polyols are prepared by using an ethylenically unsaturated polyhydric initiator to form a polyalkylene oxide. The examples set forth include dibasic acids or their derivatives, such as maleic acid. The polyol polymerization medium contains one mole of unsaturation per mole of polyol.
U.S. Pat. No. 3,652,639 likewise discloses the in situ polymerization of ethylenically unsaturated monomers in an ethylenically unsaturated polyol medium. The unsaturated polyols of this patent are produced in a manner similar to those of U.S. Pat. No. 3,823,201, as will be discussed hereinafter, except that the level of unsaturation is higher, being on the order of 1 to 3 moles of unsaturation per mole of polyol.
U.S. Pat. No. 3,823,201 discloses a method of preparing a polymer/polyol by the in situ polymerization of ethylenically unsaturated monomers in a polyol having from 0.1 to 0.7 mole of unsaturation per mole of polyol. Unsaturation at the levels set forth in the U.S. Pat. No. 3,652,639 patent were indicated as imparting unnecessarily high viscosities to the resulting polymer/polyols. The unsaturation level that is added can be introduced into the polyol by, for example, reacting it with an ethylenically unsaturated compound that is capable of adding to the polyol by reaction with the hydroxyl group, such as maleic anhydride. The polymer/polyols disclosed in U.S. Pat. No. 3,823,201 are asserted to be highly stable due to the presence of the stabilizing species which is formed via the grafting of vinyl polymer chain segments to the unsaturated polyol molecules. Certain improvements in polyurethanes using such polymer/polyols are likewise asserted. More particularly, it is stated that such polymer/polyols are surprisingly superior to those prepared from polyols having high unsaturation in regard to their low viscosities. It is further stated that polyurethane foams prepared from these graft copolymers exhibit superior load-bearing properties.
British Pat. No. 1,126,025 discloses in situ polymerization of ethylenically unsaturated monomers in a polyol having a molecular weight from 250 to 10,000, preferably from 300 to 7,000, and containing at least 0.7 double bonds per molecule. It is stated that suitable unsaturated polyols can be made by including unsaturated compounds such as unsaturated polyhydric alcohols, polycarboxylic acids, or epoxides in the reaction mixture when the polyol is formed, but that it is preferred to introduce the unsaturation by reacting a preformed polyol with an unsaturated epoxide, e.g., allyl glycidyl ether.
Japanese Pat. No. 52-80919 discloses products that are said to be useful in preparation of polyurethanes which are produced by polymerizing unsaturated polyether-esters, or copolymerizing an unsaturated polyether-ester with a vinyl monomer. The unsaturated polyether-ester is prepared by reacting a polyol having a molecular weight of 1,000 to 30,000 with a mixture of saturated and unsaturated dicarboxylic acids. It is stated that the mole ratio of saturated dicarboxylic acid to unsaturated dicarboxylic acid should be from 95/5 to 50/50 to control polymerization. In the Examples, the products are described as being very homogeneous and stable.
Japanese Patent No. 48-101494 discloses in situ polymerization of ethylenically unsaturated monomers in modified polyether polyols obtained by reacting a polyether polyol first with an unsaturated dicarboxylic acid anhydride in an amount more than 0.2 mole per mole of polyol, and then with an epoxy compound, preferably an alkylene oxide, in an amount of preferably 1.1 to 1.5 moles per mole of unsaturated dicarboxylic acid anhydride.
A further approach to production of polymer/polyols is disclosed in U.S. Pat. No. 4,198,488 to Drake et al. In the process disclosed in this patent, the monomer mixture that is polymerized in the polyol includes a minor amount of an ethylenically unsaturated dicarboxylic acid anhydride. It was theorized that some graft copolymer is produced when a portion of the dicarboxylic acid anhydride units that have polymerized into the polymer undergo a reaction with the hydroxyl groups of the polyol. And it was further theorized that the graft copolymer formed in this way acts as a stabilizer for the polymer dispersion.
While many of the above techniques have provided improved and beneficial results, there are certain cases where none of these techniques have provided products which were entirely satisfactory. Thus, for example, in some situations, the use of the blended base polyol approach results in an undue lowering of the hydroxyl number of the blend with a resultant adverse effect upon foam performance. Other approaches, while generally satisactory, are too expensive for many commercial applications, too complicated, result in color and odor problems or require foam reformulations which can create undue difficulties.
It is highly desirable for low density slab stock foam applications to be able to provide virtually scorch-free products. This can be accomplished at foam densities of about 2.5 pounds per cubic foot or so. It may also be possible with existing technology to provide foams with scorch-free characteristics at even lower densities; but, typically, the technology used either requires an economic penalty or results in less than satisfactory foam characteristics. There thus remains the need to provide techniques capable of producing, without substantial economic penalty, virtually scorch-free slab stock foams at ever decreasing densities (viz.-1.75 pounds per cubic foot or less) while maintaining satisfactory load-bearing and other foam properties.
Further, some foam applications require quite rigorous combustibility resistance. It is quite difficult with existing polymer/polyol technology to provide foams from vinyl monomer systems which meet such requirements. There thus remains an unfilled need to provide technology which can utilize vinyl monomer systems, yet satisfy these rigorous combustibility standards.
There has also been considerable development directed towards making and utilizing various polyols modified by what has been sometimes described as coupling agents. Prior patents directed to such coupled polyols include: U.S. Pat. Nos. 2,946,767; 3,054,778; 3,963,818; 4,018,815; 4,045,474; 4,061,614; 4,061,684; 4,072,704 and 4,113,785.
Coupled polyols are utilized for many applications. For example, U.S. Pat. No. 4,072,704 provides products useful as surfactants made from individual blocks of polymers and copolymers of alkylene oxides by reacting these with bifunctional compounds. U.S. Pat. No. 4,061,684 suggests the preparation of highly branched polyether polyols of high molecular weight by coupling an alkoxylated polyglycerol by reacting the sodium alcoholate of the oxyalkylated polyglycerol with, for example, a dibenzene sulfo-ester of a diol containing 2 to 6 carbon atoms. The resulting products are viscous, resinous materials, suitable for use as hydrophilic, water-swellable gels, and the like. U.S. Pat. No. 4,113,785 concerns the preparation of polyoxyalkylene polyols by reacting polyether bis-alcoholates with selected bis-epoxides, to obtain products of higher molecular weight than can be prepared using a direct oxyalkylation reaction.
Still further, the utilization of various isocyanates as coupling agents for various polyol, or polyol-type materials, has been suggested. U.S. Pat. No. 2,946,767 thus suggests the reaction of a polyisocyanate, especially a diisocyanate, with an addition product having a molecular weight of at least 1000 of an alkylene oxide, especially ethylene oxide, with a compound which contains at least 8 carbon atoms and contains only one hydrogen atom capable of reacting with an alkylene oxide, e.g.--a monoalcohol such as dodecanol. The reaction products are surface-active and are stated to be valuable assistants for the production of dispersed systems, such as emulsions or suspensions.
U.S. Pat. No. 3,054,778 suggests the reaction of polyoxyethylene glycol, or a polyoxyalkylene glycol that is water-soluble and consists predominantly of oxyethylene groups, with an organic diisocyanate in proportions and under conditions such that a substantially linear, water-soluble, film-forming, orientable, polyglycolpolyurethane resin having high tensile strength and elongation is produced. The resins are useful as warp-sizing agents, flocculating agents in aqueous media and for the production of films and fibers.
U.S. Pat. No. 3,963,681 discloses elastomer compositions prepared by using polyfunctional isocyanate, curing agent and certain polyethers having a weight average molecular weight within the range of 1000 to less than 4,500. As the polyether, it is suggested that a pre-extended polyether may be used, which is prepared by subjecting a low molecular weight polyether to reaction with a diisocyanate or by subjecting a diol compound to reaction with a diisocyanate prepolymer of polyether.
Despite all of these prior efforts, no one has suggested the utilization per se of an isocyanate-coupled polyol to provide polymer/polyols or polyurethanes utilizing such polymer/polyols. Indeed, the only known prior use of such coupled polyols in polymer/polyols is described in U.S. Pat. No. 4,242,249 to VanCleve et al., previously described, wherein one technique for forming the preformed stabilizer consisting of an anchor portion and a solvatable portion employs a solvatable portion which is the reaction product of a propylene oxide material with toluene diisocyanate. The resulting solvatable portion is then reacted with the monomer or monomers forming the anchor portion to provide the preformed stabilizer. It is stated that it is preferred that the propylene oxide material be monofunctional, although difunctional materials are satisfactory. The use of tri- or higher functionality materials, it is noted, should be avoided as extensive cross-linking has been found to occur.
It is accordingly an object of the present invention to provide polymer/polyols characterized by satisfactory stability which could not be readily made by prior techniques.
A further object provides a process for making such polymer/polyols that is relatively straight forward and does not require significant economic penalties as compared with currently known techniques.
Yet another and more specific object of this invention is to provide a technique for preparation such polymer/polyols capable of conversion to polyurethanes without imparting thereto undesirable effects upon the physical properties.
A still further object of the present invention is to provide a virtually scorch-free, relatively low density, polyurethane slab-stock foam made from a vinyl polymer, polymer/polyol.
Other objects of this invention will be apparent from the description set forth hereinafter.